could be, although prob sounds about right. Obviously each car is slightly different as will exhausts, filter etc.
My old set up of Tek 2.5 by John Banks, H&S downpipe, 2.5" decat and K&N produced 267bhp and 252 torque.
My current set up of Tek 2, H&S downpipe and 3" blitz exhaust STi panel filter gave me 280bhp and 273 torque.
I imagine you car feels really good on the road as you were expecting 280bhp so don't be too dissapointed, put your car up against simillar spec cars and my bet is there won't be much in it, if any!
Cheers
Coulster